English: August Köhler (March 4, 1866 – March 12, 1948) was a German professor and early staff member of Carl Zeiss in Jena, Germany. He is best known for his development of the microscopy technique of Köhler illumination, an important principle in optimizing microscopic resolution power by evenly illuminating the field of view. This invention revolutionized light microscope design and is widely used in traditional as well as modern digital imaging techniques today.

Köhler remained an active staff member of Zeiss for 45 years, contributing numerous innovations during this time. These include the development of a microscope operating with ultraviolet light (together with his colleague Moritz von Rohr), pioneering what would become the starting point for fluorescence microscopy, and the discovery of grid illumination, a method that would later be used in the treatment of tumors. A suggestion by Köhler led to the development of parfocal lenses which allow the specimen to remain in focus when changing objectives on a microscope. en.wikipedia.org/wiki/August_K%C3%B6hler

Images donated as part of a GLAM collaboration with Carl Zeiss Microscopy - please contact Andy Mabbett for details.